The term "engine-generator unit", as used in this patent specification, refers to the combination of a fuel burning engine and an electrical generator mechanically connected to the engine to be driven thereby. The engine may be a turbine, diesel or gas internal combustion engine, alcohol, methanol or mixed fuel engine or any other fuel burning engine, the speed and power output of which may be controlled through variations in the fuel delivery rate. The electrical generator may also vary considerably in physical characteristic, but in all cases is subject to output power control through field excitation level.
Engine-generator units are found in numerous applications, including diesel-electric locomotives, trucks, earth-moving and off-road vehicles having traction motor drives and in stationary and mobile power generating stations. Although in some applications, relatively simple mechanical isochronous governors will suffice, engine-generator units which are used in applications presenting wide variations in load and frequent transitions between load and or speed settings present a complex control problem. For example, transitions between power settings and/or load requirements in a diesel locomotive often result in smoking due to a lack of proper correlation between fuel delivery rate and engine speed. In addition, a transition in power demand can and typically does produce a response such as a power dip or overrun which is opposite in sense to the operator-generated command. These and other adverse characteristics have been typical of prior art systems.